1. Field of the Invention
The present invention relates to FM (frequency modulation) signal demodulating apparatuses, and more particularly to an improvement of FM signal demodulating apparatuses having a filter circuit for picking up a carrier signal component from a predetermined input signal.
2. Description of Background Information
In apparatuses for demodulating a frequency modulated input signal, such as an audio signal playback circuit for a video disc player system to which a frequency modulated pickup output signal is applied, filter circuits are generally provided for selectively permitting a signal having frequency around a carrier frequency before a demodulation stage of the frequency modulated input signal. However, if an impulse noise disturbance occurs in the input signal of such an apparatus, there will be a failure of the carrier signal. As an example, the carrier signal will be subject to a strong phase modulation while passing through the filter circuit due to the presence of the impulse noise which has a noise spectrum of very wide band, and also passes through the filter circuit. As a result, the quality of the demodulation signal will be greatly degraded by the presence of considerable amount of noise components.